Wireless communication system

ABSTRACT

A wireless communication system is disclosed herein. The wireless communication system may include transmitter units and a receiver. In one embodiment, each transmitter has an address and logic programmed to perform the steps of receiving a user selection and, responsive to the receiving, repeatedly transmitting a wireless selection signal until a wireless acknowledgment signal is received. The wireless selection signal may include the address and the user selection. The receiver may include means to receive a wireless selection signal and logic programmed to transmit a wireless acknowledgment signal in response to the receipt of each wireless selection signal.

PRIORITY

This application claims priority to U.S. provisional application Ser.No. 60/645,021, filed Jan. 21, 2005.

FIELD OF INVENTION

The present application relates to a wireless response system andmethod. More particularly, the present application relates to a wirelessresponse system having a plurality of transmitters and at least onereceiver and a method for using the same.

BACKGROUND

Audience response systems are employed to retrieve (or receive)responses from a group of individuals at a central location. Suchsystems may be used in classroom settings, corporate meetings, or inother gatherings of individuals. Wireless audience response systems mayinclude at least one base unit and a plurality of handheld units. Eachhandheld unit typically includes a keypad for inputting user responses.

In one known embodiment, the base unit controls communication by, forexample, polling each handheld unit. If a user has entered a responseinto the keypad, the response is transmitted to the base unit when thehandheld unit is polled. After receipt of the response, the base unitmay send an acknowledgment signal.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate various example systems, methods,and so on that illustrate various example embodiments of aspects of theinvention. It will be appreciated that the illustrated elementboundaries (e.g., boxes, groups of boxes, or other shapes in the figuresrepresent one example of the boundaries. One of ordinary skill in theart will appreciate that one element may be designed as multipleelements or that multiple elements may be designed as one element. Anelement shown as an internal component of another element may beimplemented as an external component and vice versa. The drawings maynot be to scale and the proportion of certain elements may beexaggerated for the purpose of illustration.

FIG. 1 is a simplified front plan view of one embodiment of a handhelddevice for a wireless response system;

FIG. 2 is a simplified front plan view of one embodiment of a receiverfor a wireless response system;

FIG. 3 is a simplified schematic drawing of one embodiment of a wirelessresponse system including a handheld device in communication with areceiver;

FIG. 4 is a simplified schematic drawing of one embodiment of a wirelessresponse system including a receiver in communication with a pluralityof handheld device;

FIG. 5 is a simplified flow chart of one embodiment of a method forusing a handheld device in a wireless response system;

FIG. 6 is a simplified flow chart of one embodiment of a method forusing a receiver in a wireless response system;

FIG. 7 is a simplified schematic drawing of RF profiles for a handhelddevice and a receiver in one embodiment of a wireless response system;and

FIG. 8 is a simplified illustration of one embodiment of an RF signalspread on a selected frequency band.

DETAILED DESCRIPTION

This application describes a wireless response system and method of use.The system may include at least one handheld device and a base unit. Thesystem may employ a single handheld device or several thousand handhelddevices. The handheld device may be capable of transmitting andreceiving information. The handheld device may also be referred to as atransmitter device or a handheld user transceiver.

Similarly, although the base unit is referred to as a “receiver,” it maybe capable of both transmitting and receiving information. The base unitmay be referred to as a receiver or a central transceiver.

“Address”, as used herein, includes but is not limited to one or morenetwork accessible addresses, device identifiers, electronicidentification numbers (such as EINs), IP addresses, url and ftplocations, e-mail addresses, names, a distribution list including one ormore addresses, network drive locations, account numbers or other typesof addresses that can identify a desired destination or device.

“Computer-readable medium”, as used herein, refers to any medium thatparticipates directly or indirectly in providing signals, instructionsand/or data to one or more processors for execution. Such a medium maytake many forms, including but not limited to, non-volatile media,volatile media, and transmission media. Non-volatile media may include,for example, optical disks, magnetic disks or so-called “memory sticks.”Volatile media may include dynamic memory. Transmission media mayinclude coaxial cables, copper wire, and fiber optic cables.Transmission media can also take the form of acoustic or light waves,such as those generated during radio-wave and infra-red datacommunications, or take the form of one or more groups of signals.Common forms of computer-readable media include, for example, a floppydisk, a flexible disk, hard disk, magnetic tape, or any other magneticmedium, a CD-ROM, any other optical medium, punch cards, papertape, anyother physical medium with patterns of holes, a RAM, a PROM, an EPROM, aFLASH-EPROM, any other memory chip or cartridge, a carrier wave/pulse,or any other medium from which a computer, a processor or otherelectronic device can read.

“Logic”, as used herein, includes but is not limited to hardware,firmware, software and/or combinations of each to perform a function(s)or an action(s), and/or to cause a function or action from anothercomponent. For example, based on a desired application or need, logicmay include a software controlled microprocessor, discrete logic such asan application specific integrated circuit (ASIC), a programmed logicdevice, memory device containing instructions, or the like. Logic mayalso be fully embodied as software.

“Signal”, as used herein, includes but is not limited to one or moreelectrical or optical signals, analog or digital signals, one or morecomputer or processor instructions, messages, a bit or bit stream, orother means that can be received, transmitted, and/or detected.

“Software”, as used herein, includes but is not limited to one or morecomputer readable and/or executable instructions that cause a computeror other electronic device to perform functions, actions, and/or behavein a desired manner. The instructions may be embodied in various formssuch as routines, algorithms, modules or programs including separateapplications or code from dynamically linked libraries. Software mayalso be implemented in various forms such as a stand-alone program, afunction call, a servlet, an applet, instructions stored in a memory,part of an operating system or other type of executable instructions. Itwill be appreciated by one of ordinary skill in the art that the form ofsoftware is dependent on, for example, requirements of a desiredapplication, the environment it runs on, and/or the desires of adesigner/programmer or the like.

“User”, as used herein, includes but is not limited to one or morepersons, software, computers or other devices, or combinations of these.

FIG. 1 illustrates a front plan view of one embodiment of a handhelddevice 100 for a wireless response system. In the illustratedembodiment, the handheld device 100 may include a plurality of buttons110 configured to accept a user input. In alternative embodiments, thehandheld device may employ switches, dials, an LCD touch screen, agraphical user interface, or any other known interface configured toaccept a user input.

In one embodiment, the handheld device 100 has a length of less than 5inches, a width of less than 4 inches, and a height of less than 0.75inches. In an alternative embodiment, the handheld device has a lengthof 3.3 inches, a width of 2.1 inches, and height of 0.3 inches. In otheralternative embodiments, the handheld device may be larger or smaller.

In one embodiment, the handheld device 100 is battery operated. Thebattery may be a removable battery, such as a AA or AAA size battery ora watch battery. In one embodiment, the handheld device 100 receivesoperative power from two (2) 3.0V batteries (not shown). Exemplarybatteries include, without limitation, CR2032 coin cell lithiumbatteries, CR2320 coin cell lithium batteries, or CR 1025 coin celllithium batteries. In one embodiment, the batteries have a diameter ofless than 1.25 inches and a height of less than 0.25 inches. In anotherembodiment, the batteries have a diameter of approximately 0.8 inchesand a height of approximately 0.125 inches. When such batteries are usedwith one of the above described embodiments of the handheld device 100,the handheld device 100 has a length that is less than 5 times thediameter of one battery, a width that is less than 3 times the diameterof one battery, and a height that is less than 3 times the height of onebattery. In one embodiment, two batteries may be stacked, one on top ofthe other. In another embodiment, the batteries may be placed side byside.

FIG. 2 illustrates a front plan view of one embodiment of a receiver 200for a wireless response system. In the illustrated embodiment, thereceiver 200 may include a connector 210 configured to be connected to aUSB port of a computer. In alternative embodiments, the receiver mayinclude a connector configured to be connected to a firewire or iLinkport, a serial port, or any other known type of computer port. Inanother alternative embodiment, the receiver may wirelessly communicatewith a computer via an infrared or RF transmitter. In yet anotheralternative embodiment, the receiver does not directly connect to acomputer.

With continued reference to FIG. 2, the receiver 200 may include atleast one LED 220. The LED 220 may be configured to indicate on/offstatus and transmission status. In alternative embodiments, the receivermay employ a dial, an LCD screen, or other known indicators. In anotheralternative embodiment, the receiver does not include any indicators.

In one embodiment, the receiver 200 has a length of less than 6 inches,a width of less than 2.5 inches, and a height of less than 1 inch. In analternative embodiment, the receiver 200 has a length of 3.7 inches, awidth of 1.1 inches, and a height of 0.4 inches. In other alternativeembodiments, the receiver may be larger or smaller.

FIG. 3 illustrates one embodiment of a wireless response system 300. Inthe illustrated embodiment, the system 300 includes at least onehandheld device 305 and at least one receiver 310. The handheld device305 includes a wireless data transmitter illustrated as a radiofrequency (RF) transceiver 315 configured to transmit RF signals asshown at 320 a and receive RF signals as shown at 320 b. In oneembodiment, the RF transceiver 315 may be configured as model RRRF-01,commercially available from Responsive Innovations, LLC. In analternative embodiment (not shown), the handheld device may include anRF transmitter, but not a receiver or a transceiver. In anotheralternative embodiment (not shown), the handheld device may include aninfrared (IR) source configured to transmit data and/or an IR sensorconfigured to receive data.

In one embodiment, the transceiver 315 transmits RF signals and receivesRF signals on the same frequency or channel, or on the same band offrequencies or channels. In another embodiment, the transceiver 315transmits RF signals at a first frequency (or first band of frequencies)and receives RF signals at a second frequency (or second band offrequencies).

As shown in FIG. 3, the handheld device 305 includes an input interface325. Exemplary input interfaces include a keypad, an LCD touchpad,dials, toggle switches, levers, knobs, buttons, or any other appropriatecontrol or input mechanisms.

In one embodiment, the transceiver 315 may transmit and receive RFtransmissions on one of a plurality of different frequencies. The usermay select the frequency through the input interface 325. In thismanner, the user may select a frequency that has little or no local RFactivity to avoid interference. In one embodiment, the user may select afrequency from 82 different frequencies. In an alternative embodiment,the user may select from more or fewer frequencies.

The input interface 325 is in communication with processing logic 330.When a user inputs a selection into the input interface 325, the userselection may be communicated to the processing logic 330. Theprocessing logic 330 may then generate and format a signal fortransmission. In one embodiment, the signal may include a stored address335, and the user selection. The address 335 may be a number, a sequenceof alphanumeric characters, a sequence of ASCII characters, and thelike. In one embodiment, the address 335 is permanently assigned to ahandheld device 305 and stored in a computer-readable medium, such as amemory 340.

In an alternative embodiment (not shown), an address may be generatedupon the occurrence of a predetermined event. For example, theprocessing logic 330 or other logic may randomly generate an address 335each time a user inputs a selection or after a predetermined number ofselections. In another embodiment, the receiver 310 may assign anaddress to each handheld device 305, or the user may enter anidentifier.

With continued reference to FIG. 3, the processing logic 330 is shown tobe in communication with signal generating logic 345. After theprocessing logic retrieves the address 335, the processing logic 330sends the user selection and the address 335 to the signal generatinglogic 345. The signal generating logic 345 may generate an RF signalthat encodes the user selection and the address. In an alternativeembodiment (not shown), the processing logic 330 may perform the step ofgenerating an RF signal.

The processing logic 330 may also be in communication with the RFtransceiver 315. After the RF signal is generated, the processing logic330 instructs the RF transceiver 315 to transmit the RF signal as shownat 320 a. The RF signal may also be referred to as a wireless selectionsignal. In one embodiment, the RF signal is transmitted until anacknowledgment signal is received or for a predetermined amount of time.

As illustrated in FIG. 3, the processing logic 330 may be incommunication with a transmission interval logic 350. The transmissioninterval logic 350 generates a transmission interval. The transmissioninterval is an amount of time or clock cycles that elapse betweentransmission attempts of the RF signal. In one embodiment, thetransmission interval is generated on the order of microseconds. Inalternative embodiments, the transmission interval is generated on theorder of seconds, milliseconds, nanoseconds, picoseconds, femtoseconds,attoseconds, or any other known measurement of time. The transmissioninterval can be optimized by a number of factors, such as: the number ofhandheld devices, the number of receivers, the number of users, thefrequency of which questions are asked by a moderator, the frequency ofthe RF signal, the amount of data being transmitted, and the type ofdata being transmitted.

In one embodiment, the transmission interval logic 350 generates atransmission interval by generating a random number. In anotherembodiment, the transmission interval is calculated according to amathematical function. For example, the transmission interval may becalculated by multiplying the address 335 by programmed constant or by arandom number. In another embodiment (not shown), the transmissioninterval may be generated by the processing logic 330. In yet anotheralternative embodiment (not shown), a unique transmission interval maybe a fixed, predetermined number and stored in memory 340.

In another alternative embodiment, the time interval may vary with eachretransmission of a selection. For example, the time interval may becomeprogressively longer after each retransmission. In one embodiment, thetransmission interval may be calculated according to the formulat_(n)=r+n(ε), where t_(n) is the time interval for the n^(th) iteration,r is a random number that is either predetermined or generated with eachuser selection, n is the number of current iterations, and ε is a smallnumber relative to r. In this embodiment, for example, the transmissioninterval after the first transmission may be 5 ms, the transmissioninterval after the first re-transmission may be 5 ms+100 μs, thetransmission interval after the second re-transmission may be 5 ms+200μs, etc.

The handheld device 305 transmits the RF signal at a user selectedfrequency or at a default frequency, according to the transmissioninterval. In other words, the RF transceiver 315 transmits the RFsignal, then pauses for a length of time equal to the transmissioninterval, then repeats the transmission. This process may be repeatedfor a predetermined number of transmissions, a predetermined length oftime, or until an acknowledgment signal is received. In one embodiment,the process repeats until the first occurrence of: (a) the receipt of anacknowledgment signal or (b) eight (8) seconds elapse after the first RFtransmission. In an alternative embodiment, the predetermined length oftime may be five (5) seconds. In another alternative embodiment, thereis no predetermined length of time for terminating the transmission. Inyet another alternative embodiment, the predetermined length of time maybe programmable by a user.

The transmission interval may serve several functions. For example,using a transmission interval may conserve power, because sending atransmission intermittently may use less power than sending a continuoustransmission. Further, when a single receiver 310 is receiving RFsignals from a plurality of handheld devices 305, the use of differenttransmission intervals staggers the RF signals, such that they willarrive at the receiver 310 at different times. Additionally, some knowntransceivers may not be capable of simultaneous or near simultaneousreceiving and transmitting of an RF signal. If such a transceiver isemployed, the transmission interval allows the RF transceiver 315 toreceive an acknowledgement signal at a time when it is not transmittingan RF signal.

With continued reference to FIG. 3, the handheld device also includes anoutput interface 355. In one embodiment, the output interface 355indicates operating status to a user such as: that a signal is beingtransmitted, that an acknowledgment has been received, that user entryhas been confirmed, and the like. In such an embodiment, one or moreLEDs, an LCD, or other display may serve as an output interface 355.

In one exemplary embodiment (not shown), the handheld device 305 employsa three color LED arrangement selected for the low power requirements ofLED technology. In this embodiment, the LED flashes a first color (suchas amber) to indicate that the handheld device 305 is transmitting an RFsignal. The LED emits a solid (i.e., non-flashing) second color (such asgreen) to indicate that an acknowledgement signal has been received andthe data has been accepted by the receiver 310. The LED emits a solidthird color (such as red) to indicate that no acknowledgement signal hasbeen received and the transmission has been terminated unsuccessfully.In an alternative embodiment, the handheld device 305 may employ afourth LED display to indicate that an acknowledgment signal isreceived, but the user selection was not accepted by the receiver 310.

In another embodiment, the output interface 355 may include an LCD. Afirst display message indicates that the handheld device 305 istransmitting a signal, a second display message indicates that anacknowledgment has been received, and a third display message indicatesthat no acknowledgment has been received and the transmission has beenterminated. Additionally, the LCD screen may display the user selectionalong with the transmission status.

In one embodiment, the handheld device 305 includes a power source 360,such as a battery. The power source 360 may be a removable battery, suchas a AA or AAA size battery or a watch battery, which can be replacedwhen the power runs low. In one embodiment, the power source 360includes two (2) 3.0V batteries. Exemplary batteries include, withoutlimitation, CR2032 coin cell lithium batteries, CR2320 coin cell lithiumbatteries, or CR 1025 coin cell lithium batteries.

In one embodiment, the handheld device 305 can transmit an RF signalwhen supplied with a current of 10.5 mA and can receive an RF signalwhen supplied with a current of 19 mA. In other embodiments, thehandheld device can transmit an RF signal when supplied with a currentof less than 15 mA and can receive an RF signal when supplied with acurrent of less than 25 mA.

Alternatively, the power source 360 may be more permanently fixed withinthe handheld device 305 and the handheld device 305 may be plugged intoan external power source to recharge the power source 360. In anotherembodiment (not shown), the handheld device may alternatively beconfigured to be plugged into an external power source or employphotovoltaic panels.

FIG. 4 illustrates a simplified schematic drawing of one embodiment of awireless response system 400, having a receiver 405 in communicationwith a plurality of handheld devices 410A-N. The handheld devices 410A-Nmay be substantially similar to the handheld device 305 illustrated inFIG. 3. It should be understood that the receiver 405 may be in datacommunication with a single handheld device or many handheld devices.

As shown in FIG. 4, the receiver 405 includes an RF transceiver 415configured to receive an RF signal as shown at 420 a and send an RFsignal as shown at 420 b. In an alternative embodiment (not shown), thereceiver may include an RF receiver, but not a transmitter or atransceiver. In another alternative embodiment (not shown), the receivermay include an infrared (IR) sensor configured to receive data and/or anIR source configured to transmit data.

The receiver 405 further includes processing logic 425 in datacommunication with signal decoding logic 430. In this embodiment, when asignal is received by the RF transceiver, it is communicated to theprocessing logic 425. The processing logic may instruct the signaldecoding logic 430 to decode and parse the signal. The signal decodinglogic 430 decodes the signal and parses the signal into componentsincluding a user selection and an address. In an alternative embodiment(not shown), the processing logic 425 may decode and parse the signal.

In one embodiment (not shown), the receiver may have an ID. Theprocessing logic may be configured to only accept signals that containthe receiver ID, thus ensuring that any collected data is not skewed byspurious signals. In one embodiment, a replacement receiver may have thesame ID as a first receiver. In such an embodiment, the replacementreceiver would accept signals from the handheld devices, without theneed for reprogramming the handheld devices. In another embodiment, allmanufactured receivers may have the same ID.

After the signal has been successfully decoded and parsed, theprocessing logic 425 may generate an acknowledgment signal thatcontains, for example, the address and an acknowledgment indicator. Theacknowledgment signal may also include an indication of whether the userselection was accepted. The processing logic 425 may also instruct theRF transceiver 415 to communicate the acknowledgment signal overcommunication link 420 b.

With continued reference to FIG. 4, the receiver 405 also includes acomputer-readable medium such as a memory 435, configured, for example,as RAM, EEPROM, or other types of writable memory. In one embodiment,the user selection and/or the address are stored in the memory 435 afterthe signal has been decoded and parsed by the signal decoding logic 430.The storing of the user selection and/or the address may occur before,after, or concurrently with the transmission of the acknowledgmentsignal. In an alternative embodiment (not shown), the receiver does nothave a writable memory and the user selection and unique identifier areinstead only communicated to an external computer.

As further shown in FIG. 4, the receiver 405 includes an outputinterface 440. In the illustrated embodiment the output interface 440 isan interface for a computer 445. The computer 445 may be a PC, a laptop,a graphing calculator, or any other type of computer. The outputinterface 440 is in communication with the computer 445 via a hardwireconnection 450. The hardwire connection 450 may connect to a USB port, aserial port, a firewire or iLink port, or any other type of port. In analternative embodiment (not shown), the output interface 440 is incommunication with the computer 445 via a wireless connection.

In the illustrated embodiment, the receiver 405 further includes aninput interface 455. In an alternative embodiment (not shown), thereceiver includes a single interface for both input and output. Thereceiver 405 may receive instructions from the computer 445 through theinput interface 455, such as instructions to wipe the memory 435. In oneembodiment, the input interface 455 receives power from the computer 445through the connection 450. In an alternative embodiment (not shown),the receiver 405 may include an internal power source, such as a batteryor external power means.

In an alternative embodiment (not shown), the receiver is not connectedto an external computer. Instead, the output interface 440 is a display,such as an LCD display. In such an embodiment, the user selection and/orthe address may be displayed on the output interface 440. In anotheralternative embodiment (not shown), the handheld device is not incommunication with a computer during the communication of RF signals.Instead, data may be stored in the memory 435 and transferred to acomputer 445 at a later time.

FIG. 5 illustrates a flow chart diagram for an exemplary method 500 forusing a handheld device in a wireless communication system. The usermakes a selection, step 505, by selecting a button, turning a dial, etc.on the handheld device. After the user has made a selection, thehandheld device communicates a signal that includes the user selectionand an address, step 510.

The handheld device then waits for an acknowledgment signal, step 515.If an acknowledgment signal is not received, the handheld devicegenerates or retrieves from memory a transmission interval, step 520,for example, as described above in reference to FIG. 3. The handhelddevice then determines whether the transmission interval has elapsed,step 525. If the transmission interval has not elapsed, the handhelddevice continues to wait for an acknowledgment signal, step 515. If thetransmission interval has elapsed, then the handheld device determineswhether a predetermined transmission time limit has elapsed, step 530.If the predetermined transmission time limit has elapsed, the handhelddevice indicates that no acknowledgment was received, step 535, and thehandheld device terminates transmission, step 540. If the predeterminedtransmission time limit has not elapsed, the handheld devicere-transmits the signal, step 510. The handheld device then waits againfor an acknowledgment signal, step 515.

Once the handheld device receives an acknowledgment signal, step 515, itdetermines whether the acknowledgment signal indicates that the data wasaccepted, step 545. If the data was accepted, the handheld deviceindicates receipt and acceptance, step 550, and terminates transmission,step 540. If the data was not accepted, the handheld device indicatesreceipt and non-acceptance, step 555, and terminates transmission.

In one embodiment, the handheld device transmits an RF signal andreceives an acknowledgment RF signal at the same frequency, or on thesame frequency band. In another embodiment (not shown), the handhelddevice transmits an RF signal at a first frequency (or first frequencyband) and receives an acknowledgment RF signal at a second frequency (orsecond frequency band) different from the first frequency (or firstfrequency band). In such an embodiment, the handheld device may transmitand receive signals concurrently.

FIG. 6 illustrates a flow chart diagram for an exemplary method 600 forusing a receiver in a wireless communication system. The receiver isfirst powered on, step 610, and enters a receive mode, step 620. In oneembodiment, the receiver is powered on merely by plugging it into a USBport of a computer. While the receiver is in receive mode, it waits toreceive a signal on a communication link, step 630. If no signal isreceived, the receiver remains in receive mode, step 620. Once a signalis received, the receiver may derive components from the signal such asuser selected data or address data, step 640.

After the data has been derived, the receiver determines whether some orall of the data can be accepted, step 650. If the data is accepted, thereceiver transmits an acknowledgment of receipt and acceptance, step660, and the data is stored in the receiver's memory and/or transmittedto an external processor, step 670. The receiver then returns to receivemode, step 620. In another embodiment (not shown), step 670 may beperformed before or concurrently with step 660. If the data isdetermined to be unacceptable, step 650, the receiver may transmit anacknowledgment of receipt and non-acceptance of data, step 680. Thereceiver then returns to receive mode, step 620.

FIG. 7 illustrates a simplified schematic drawing of RF profiles 700 aof a handheld device 705 in one embodiment of a wireless responsesystem. In alternative embodiments, a plurality of handheld devices areemployed. In the illustrated embodiment, the handheld device 705 makesno transmission until it receives a selection from a user. Thus, in RFprofile 700 a, there is a distinct period of no RF transmission 710.Upon a user entering a selection, the handheld device 705 transmits afirst RF signal 720 ₁ at a frequency f thus initiating a first period ofRF transmissions 725. The first RF signal 720 ₁ includes a userselection and an address, such as a unique address. In one embodiment,the first RF signal 720 ₁ lasts for a duration of 100 μs. The durationis a function of the amount and type of data and the frequency f.

After the handheld device 705 transmits the first RF signal 720 ₁, theRF profile 700 a includes no RF signals for a period equal to atransmission interval 730. The transmission interval 730 may begenerated or retrieved from memory, for example, as explained above inreference to FIG. 3. In one embodiment, the transmission interval lastsfor a duration of 5 ms. After the transmission interval 730, the RFprofile 700 a includes additional RF signals 720 _(2-n). Each RF signal720 _(2-n) is identical to the first RF signal 720 ₁, and is followed bya transmission interval 730. Thus, in one embodiment, during the firstperiod of RF transmissions 710, there is a transmission frequency of onetransmission every 5 ms. In another embodiment, the transmissioninterval 730 is variable. For example, the transmission interval 730 maybe 5 ms after the first RF signal 720 ₁, then 5 ms+100 μs after thesecond RF signal 720 ₂, . . . and 5 ms+((n-1)*100)μs after the n^(th) RFsignal 720 _(n).

FIG. 7 further illustrates an RF profile 700 b of a receiver 735 in oneembodiment of a wireless response system. During the first period of RFtransmissions described above, the receiver 735 receives one of the RFsignals 720 _(1-n) transmitted by the handheld device 705, as shown at740. The receiver 735 makes no transmission until it receives an RFsignal.

Upon receipt of an RF signal at 740, the receiver 735 may identify userselection data and address data in the RF signal and determine whetherto accept the user selection data. The receiver 735 then generatesreturn data that includes the address data, as shown at 745. Thereceiver 735 communicates return data as at least one RF return signal750 at the frequency f, thus initiating a second period of RFtransmissions 755 that overlaps with the first period of RFtransmissions 710. In one embodiment, the return signal 750 lasts for aduration of 100 μs.

The receiver 735 transmits a predetermined number of return signals 750then terminates the second period of RF transmissions 755. In theillustrated embodiment, the receiver 735 transmits a single returnsignal 750. In another embodiment (not shown), the receiver transmitsmultiple return signals, wherein each return signal is followed by apredetermined transmission interval or a randomly generated timeinterval.

Upon receipt of the return signal 750, as shown at 760, the handhelddevice 705 terminates the first period of RF transmissions 710.Alternatively, if no return signal is received, the handheld device 705may automatically terminate the first period of RF transmissions 710after a predetermined time elapses. In one embodiment, the predeterminedtime limit is eight (8) seconds. In this embodiment, the first period ofRF transmissions 710 has a duration of 100 microseconds to eight (8)seconds.

After the first and second periods of RF transmissions 725,755 areterminated, another distinct period of no RF transmissions follows. Inan alternative embodiment (not shown), the handheld device 710 maytransmit an RF signal at a first frequency and the receiver 740 maytransmit an acknowledgment signal at a second frequency.

FIG. 8 illustrates one embodiment of an RF signal spread 800 on aselected frequency band. In this embodiment, the RF signal spread 800covers a range of frequencies from f_(o) to f_(n). When a handhelddevice or a receiver transmits on a selected frequency band, a signal istransmitted that may be centered on a frequency f_(c) while spread overf_(o) to f_(n). The signal is strongest, and therefore has the highestamplitude, on frequency f_(c) at the center of the frequency band. Thesignal amplitude decreases at frequencies further from f_(c), as shownin the illustrated embodiment. Both a handheld device and a receiver maytransmit signals over this illustrated RF signal spread, or the handhelddevice and the receiver may transmit signals centered on differentfrequencies.

While the present application has been illustrated by the description ofembodiments thereof, and while the embodiments have been described insome detail, it is not the intention of the applicants to restrict or inany way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. Therefore, the application, in its broader aspects,is not limited to the specific details, the representative apparatus, onthe illustrative embodiments shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of the applicant's general inventive concept.

1. A wireless communication system comprising: a plurality of handhelddevices, each handheld device including: a transmitter, acomputer-readable medium configured to store an address, an inputselection control, and a processor configured to receive a userselection from the input selection control; and, upon receipt of theuser selection, communicate instructions to the transmitter to transmitan RF signal encoding the address and the user selection according to adefined RF profile; and a receiver device including: a transceiver, acomputer-readable medium, and a processor configured to decode the RFsignal into the address and the user selection following receipt by thetransceiver, store the user selection in the computer-readable medium,generate an acknowledgment including a representation of the address,and communicate instructions to the transceiver to transmit theacknowledgement according to the defined RF profile.
 2. The system ofclaim 1, wherein the defined RF profile includes a transmission intervalseparating periodic retransmissions of the RF signal.
 3. The system ofclaim 1, wherein the defined RF profile comprises: a distinct period ofno RF transmission; and a first period of RF transmission correspondingto transmission of the RF signal, where the first period of RFtransmission occurs after the distinct period of no RF transmission andis responsive to receipt of the user selection at the handheld device.4. The system of claim 3, wherein the defined RF profile furthercomprises: a second period of RF transmission corresponding totransmission of the acknowledge signal, where the second period of RFtransmission occurs after the start of the first period and isresponsive to receipt of the RF signal.
 5. The system of claim 3,wherein the first period of RF transmission has a duration of 100microseconds to 8 seconds.
 6. The RF profile as set forth in claim 4,wherein the second period has a duration of 100 microseconds.
 7. Thesystem of claim 4, wherein the second period of RF transmission isfollowed by a distinct period of no RF transmission.
 8. The system ofclaim 1, wherein each handheld device further includes a power sourceconfigured to provide no more than 25 mA DC current.
 9. The system ofclaim 8, wherein the power source includes at least one battery.
 10. Thesystem of claim 8, wherein the power source includes two 3.0 Voltbatteries.
 11. The system of claim 1, wherein the transmitter isconfigured to draw a DC current of less than 15 mA when transmitting theRF signal and a DC current of less than 25 mA when receiving theacknowledgment.
 12. The system of claim 1, wherein the transmitter isconfigured to draw a DC current of 10.5 mA when transmitting the RFsignal and a DC current of 19 mA when receiving the acknowledgment. 13.The system of claim 1, wherein the receiver device is configured to drawa DC current less than 25 mA.
 14. The system of claim 13, wherein thereceiver device is adapted to draw the DC current from a power sourceconnectable to, but external from the receiver device.
 15. The system ofclaim 13, wherein the receiver device is configured to draw a DC currentof less than 25 mA when receiving the RF signal and a DC current of lessthan 15 mA when transmitting the acknowledgment.
 16. The system of claim13, wherein the receiver device is configured to draw a DC current of 19mA when receiving the RF signal and a DC current of 10.5 mA whentransmitting the acknowledgment.
 17. A battery-operated handheld deviceconfigured to receive a selection from a user and, responsive to theuser selection, transmit an RF signal including a representation of theuser selection, and receive an RF acknowledgment signal, the devicecomprising: a user interface configured to receive a user input;processing logic configured to identify the user input as at least oneof an RF frequency selection and a user selection; signal generatinglogic configured to generate an RF signal representation of the userselection; an RF transceiver configured to draw less than 25 mA DCcurrent while sending and receiving RF signals; and a housing configuredto house the processing logic, the signal generating logic, the RFtransceiver, and at least one operably connected battery, wherein thehousing has a length that is less than 5 times the diameter of the atleast one battery, a width that is less than 3 times the diameter of theat least one battery, and a height that is less than 3 times the heightof the at least one battery.
 18. The device of claim 17, wherein the atleast one battery is a coin cell lithium battery.
 19. The device ofclaim 17, wherein the at least one battery has a diameter of less than1.25 inches and a height of less than 0.25 inches.
 20. The device ofclaim 17, wherein the at least one battery has a diameter ofapproximately 0.8 inches and a height of approximately 0.125 inches. 21.The device of claim 17, wherein the housing has a length of less than 5inches, a width of less than 4 inches, and a height of less than 0.75inches.
 22. The device of claim 17, wherein the housing has a length of3.3 inches, a width of 2.1 inches, and height of 0.3 inches.